Ingredients

How Do We Know Something Is Good At Moisturising?

how do we know something is good at moisturising

I was listening to the perky pair of Randy and Perry over on the Beauty Brains the other day. They were answering a question about whether or not lanolin was a good moisturiser. They replied that it was indeed but that mineral oil was better. I knew straight away why they had said that and what they were was true enough in as far as it went, but nonetheless I think they were wrong to suggest that mineral oil is actually better. But it is going to be involved to explain why, so maybe get a sandwich.

The way things like lanolin, mineral oil and vegetable oils have a moisturising effect is by forming a layer on the surface of the skin that holds the moisture in. It isn’t so very different to wrapping your skin in cling film.

The precise nature of the film that the oil produces determine how good it is at moisturising. There are a number of ways in which this effect can be measured. For example you can apply to some oil to the skin and measure the moisture content by passing a small electric current through the skin. Moist skin is more conductive to electricity so the greater the conductivity the more powerful the moisturising effect your oil has. This is a reasonable model in as far as it goes.

But it is open to some objections. For a start the conductivity might be affected directly by the oil itself. And if you are testing the oil as a component of a cream there is every chance that the other components will affect the conductivity.

Another method is simply to put a film across a container with water in it and then apply a layer of the oil to the film. You can get films that are synthetic versions of skin. There is no reason this shouldn’t give an idea of how well an oil works, but I have done this kind of experiment myself and the practice difficulties are, well, difficult.

These two methods are the most direct, but there are other ways where you track what are assumed to be the beneficial effects of moisturisation, such as how elastic the skin is or how smooth it is on the surface.

But while these techniques have their uses, none of them are totally satisfactory. The skin is a complex organ.  You can tell a certain amount about what a wine tastes like by analysing how much sugar and tannin it contains, but you don’t really get either the whole picture.  It is a bit like that measuring the effect of something applied to the skin. The numbers you get from the instrument are an indication, but the actual experience is rather more involved.

So to my mind the only way you can really tell whether or not something is moisturising is to try it out on your own skin over a period of time.  This can’t generate the kind of data you can publish in a scientific paper.  But it is a better guide to coming up with good products.  So is mineral oil the best moisturiser?  It is certainly a good one, but I wouldn’t say it was hugely better than vegetable oils.  But on my skin the star moisturiser is lanolin.  It is a bit smelly and it is difficult to rub into the skin.  It also leaves the finger you have used to apply it unusable for any other purpose for a few minutes after you have applied it.  But for moisturising effect it is great.  You notice it more quickly than with other products and the effect lasts longer.

That is my feeling anyway.  Lanolin has been out of fashion for a very long time now and it still appears on lists of things that companies choose to avoid.  And as the Brains boys say, mineral oil scores higher in reported moisturising power.  I think we are all missing a trick, but I can’t prove it.

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